This invention relates generally to the treatment of spinal conditions, and more particularly, to the treatment of spinal stenosis using devices for implantation between adjacent spinous processes.
The clinical syndrome of neurogenic intermittent claudication due to lumbar spinal stenosis is a frequent source of pain in the lower back and extremities, leading to impaired walking, and causing other forms of disability in the elderly. Although the incidence and prevalence of symptomatic lumbar spinal stenosis have not been established, this condition is the most frequent indication of spinal surgery in patients older than 65 years of age.
Lumbar spinal stenosis is a condition of the spine characterized by a narrowing of the lumbar spinal canal. With spinal stenosis, the spinal canal narrows and pinches the spinal cord and nerves, causing pain in the back and legs. It is estimated that approximately 5 in 10,000 people develop lumbar spinal stenosis each year. For patients who seek the aid of a physician for back pain, approximately 12%-15% are diagnosed as having lumbar spinal stenosis.
Common treatments for lumbar spinal stenosis include physical therapy (including changes in posture), medication, and occasionally surgery. Changes in posture and physical therapy may be effective in flexing the spine to decompress and enlarge the space available to the spinal cord and nerves—thus relieving pressure on pinched nerves. Medications such as NSAIDS and other anti-inflammatory medications are often used to alleviate pain, although they are not typically effective at addressing spinal compression, which is the cause of the pain.
Surgical treatments are more aggressive than medication or physical therapy, and in appropriate cases surgery may be the best way to achieve lessening of the symptoms of lumbar spinal stenosis. The principal goal of surgery is to decompress the central spinal canal and the neural foramina, creating more space and eliminating pressure on the spinal nerve roots. The most common surgery for treatment of lumbar spinal stenosis is direct decompression via a laminectomy and partial facetectomy. In this procedure, the patient is given a general anesthesia as an incision is made in the patient to access the spine. The lamina of one or more vertebrae is removed to create more space for the nerves. The intervertebral disc may also be removed, and the adjacent vertebrae may be fused to strengthen the unstable segments. The success rate of decompressive laminectomy has been reported to be in excess of 65%. A significant reduction of the symptoms of lumbar spinal stenosis is also achieved in many of these cases.
Alternatively, the vertebrae can be distracted and an interspinous process device implanted between adjacent spinous processes of the vertebrae to maintain the desired separation between the vertebral segments. Such interspinous process devices typically work for their intended purposes, but some could be improved. For example, many currently available interspinous process devices are challenging to properly place between adjacent spinous processes because of the space limitations in that area, which is filled with various muscles, ligaments, bone and other tissue. Some devices require a posterior to anterior approach. These types of devices are undesirable because they require that both the interspinous ligament and the supraspinous ligament be cut, or otherwise manipulated to allow the physician to gain access to the space between adjacent interspinous processes. In any surgical procedure, it is desirable to minimize trauma to surrounding tissue as much as possible in order to minimize recovery time for the patient and to provide the patient with the greatest chance for a successful outcome.
In view of the challenges with interspinous process devices that require a posterior to anterior approach, some devices have been designed that allow for a lateral approach. Some of these devices are significant improvements over those devices that require a direct posterior to anterior approach. However, even some devices that allow for a lateral approach to the space between adjacent spinous processes have challenges. As noted above, the space between adjacent spinous processes is confined. Thus it is difficult for the surgeon to manipulate the device to ensure that it is properly located in the space and to ensure that the device remains properly positioned therein. Where additional manipulation of the device is necessary to ensure that the device remains properly positioned in the desired space, the spatial limitations would be a factor militating against ease of insertion.
Thus, a need exists for improvements in interspinous process devices.